<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    /* 并集选择器 */
    /* 逗号分隔 */
    p,
    h1,
    h2 {
      font-size: 30px;
      color: rgb(255, 0, 0);
    }
  </style>
</head>

<body>
  <p>我是p元素</p>
  <h1>我是h1元素</h1>
  <h2>我是h2元素</h2>
</body>

</html>